Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Microorganisms and viruses are responsible for a variety of diseases and disorders in humans and animals, including many dermatological disorders. Dermatophytes, for example, are a group of fungi that cause skin diseases in animals and humans. They include the genera Microsporum, Epidermophyton and Trichophyton. Tinea is a term used to describe a variety of skin mycoses including tinea pedis (commonly referred to as “athlete's foot”), tinea corporis (infections of the trunk, arms and legs), tinea manuum (infections of the finger webs), tinea cruris (infections of the groin), tinea barbae (infections of the neck) and tinea capitis (infections of the scalp).
Viruses are also responsible for a number of skin infections in animals and humans. Skin lesions such as warts, cold sores and shingles are often caused by viral infections. Most primary viral infections arise from one of three groups of viruses; poxviruses (poxviridae), herpesviruses (herpesviridae) and human papillomaviruses (papillomaviridae).
Common warts are a benign form of tumour typically caused by human papillomaviruses (HPV). Some strains of HPV, however, are also etiological agents in dysplasia and carcinomas in the oral and genital mucosa.
Molluscuum contagiosum is a type of poxvirus that causes skin lesions, sometimes referred to as water warts. Water warts are characterised by small, discrete, lobulated epidermal outgrowths that occur at various locations on the body.
Herpes zoster, commonly referred to as shingles, is a skin lesion caused by infection from the herpesviridae family of viruses. Shingles is often characterised by a painful rash and localised blistering which can last for several months.
Herpes Simplex Type 1 (HSV1) and Herpes Simplex Type 2 (HSV2) are etiological agents of cold sores and genital herpes, respectively. However, both types of herpes simplex virus (HSV) can be present on the mouth and genital areas, and it is possible for an individual to be infected by both HSV1 and HSV2. Infection by one strain does not render an individual immune to the other.
Recurrent outbreaks of HSV often follow a staged progression involving prodrome, vesicle formation, ulceration, crusting and healing. Prodrome is typically characterised by a short period of tingling, itching, numbness or burning with no clearly visible indication of an infection or outbreak. Vesicle formation involves the development of fluid-filled blisters, often in a cluster, and usually surrounded by sore, red skin. Ulceration occurs when the blisters open to form painful ulcers or open sores often with a yellow crust at the edges of the sore. At the crusting stage, weeping sores or ulcers are covered by a crust or scab. Healing involves the disappearance of the crust, swelling, pain and itching. Skin eruptions caused by viral infection, particularly HSV, generally have a normal infective course that lasts from between 10 and 60 days depending on the species of infective virus and the anatomical location of the infection.
After an initial outbreak of HSV, the virus may lie dormant in the skin or in nerve tissue until triggered to cause a new eruption or site infection. Triggers may include stress, fever, sunlight, hormonal changes or certain foods or drugs. When the virus is reactivated, it typically causes a sore at the site where it first entered the body.
Presently, there is no effective vaccine to prevent herpes infection. Moreover, the ability of the herpes virus to retreat into the nervous system makes it difficult to eliminate from the body. Systemic treatment of viral and fungal infections, although effective in some cases, may be associated with health risks including cardiac or hepatic toxicity, nausea, headaches and adverse drug interactions. Physical treatments such as cryotherapy, laser therapy and surgical removal, while also effective in some cases, can be painful and distressing, particularly for children, and may increase the likelihood of scar tissue formation. Topical antiviral formulations have also been developed, however, many suffer from problems such as poor stability leading to limited shelf-life, susceptibility to freezing, poor active ingredient solubility or inefficient delivery of the active ingredient.
In this context, there is a need for alternative methods and compositions for treating skin and mucosal membrane infections, and in particular, infections caused by viruses and fungi. It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art or to provide a useful alternative.